cultivated rhododendros : spreading threat?
 

Is there any need for alarm?

We used to have six massive rhododendron bushes in our front garden that
produced a wonderful wall of colours about this time each year. Over
the course of many years, never once did we find a little rhododendron
sapling growing anywhere else in our garden, or for that matter in the
surrounding fields. Those rhodies simply never spread - despite our
garden and all of the surrounding land being highly acidic, quite
temperate, and ideal for the growing of rhodies..

Then we moved house about three years ago and missed the wall of the
colour, so we planted a dozen small cultivated rhododendrons purchased
from a local nursery.

Along comes a neighbour yesterday with fear writ large all across her
brow and she warns us we had better cut every single flower off once
the petals have fallen OR there'll be rhododendrons everywhere and local
farmers will be furious with us!

There are no other rhododendrons in gardens in this area, though
largely, I suspect, because most of this area is more alkaline than
acidic. We are fortunate in that our little patch is quite acidic.
Could it be that the fear of cultivated rhododendrons in this area has
resulted from the fact that people can't grow them here and are ignorant
of them?

Have done a brief google on this subject and found that "Rhododendron
ponticum" can spread.

Thanks.

Eddy.

cultivated rhododendros : spreading threat?
 

In article ,
Eddy wrote:

Along comes a neighbour yesterday with fear writ large all across her
brow and she warns us we had better cut every single flower off once
the petals have fallen OR there'll be rhododendrons everywhere and local
farmers will be furious with us!

There are no other rhododendrons in gardens in this area, though
largely, I suspect, because most of this area is more alkaline than
acidic. We are fortunate in that our little patch is quite acidic.
Could it be that the fear of cultivated rhododendrons in this area has
resulted from the fact that people can't grow them here and are ignorant
of them?

No. It's a result of the media hysteria. If rhododendrons don't
grow well locally, they won't naturalise - and acidity is only one
of the factors that they need. Outside SOME parts of the far west,
and a FEW parts of the south, even R. ponticum will have trouble
when faced with real competition. Despite claims, its spread is
NOT limited by the fact that "it hasn't got here yet", but by the
fact that it won't spread to the relevant locations.


Regards,
Nick Maclaren.

cultivated rhododendros : spreading threat?
 

"Eddy" wrote in message
...

Is there any need for alarm?

We used to have six massive rhododendron bushes in our front garden that
produced a wonderful wall of colours about this time each year. Over
the course of many years, never once did we find a little rhododendron
sapling growing anywhere else in our garden, or for that matter in the
surrounding fields. Those rhodies simply never spread - despite our
garden and all of the surrounding land being highly acidic, quite
temperate, and ideal for the growing of rhodies..

Then we moved house about three years ago and missed the wall of the
colour, so we planted a dozen small cultivated rhododendrons purchased
from a local nursery.

Along comes a neighbour yesterday with fear writ large all across her
brow and she warns us we had better cut every single flower off once
the petals have fallen OR there'll be rhododendrons everywhere and local
farmers will be furious with us!

There are no other rhododendrons in gardens in this area, though
largely, I suspect, because most of this area is more alkaline than
acidic. We are fortunate in that our little patch is quite acidic.
Could it be that the fear of cultivated rhododendrons in this area has
resulted from the fact that people can't grow them here and are ignorant
of them?

Have done a brief google on this subject and found that "Rhododendron
ponticum" can spread.

Thanks.

Eddy.

Most of those big'n'blousy rhodos are hybrids that set little or no viable
seed. They won't spread. Even the true species (other than ponticum) aren't
particularly efficient at spreading by seed in a short time.

The main thing to remember with some rhodos is that they "poison" the soil
beneath them and make it very difficult for other plants to germinate their
seeds or get established once they have germinated.

As to people's fear of cultivated rhodos, why add "of them" at the end? ;-)

--

Jeff

cultivated rhododendros : spreading threat?
 

In message ,
writes
In article ,
Eddy wrote:

Along comes a neighbour yesterday with fear writ large all across her
brow and she warns us we had better cut every single flower off once
the petals have fallen OR there'll be rhododendrons everywhere and local
farmers will be furious with us!

There are no other rhododendrons in gardens in this area, though
largely, I suspect, because most of this area is more alkaline than
acidic. We are fortunate in that our little patch is quite acidic.
Could it be that the fear of cultivated rhododendrons in this area has
resulted from the fact that people can't grow them here and are ignorant
of them?

It's only Rhododendron ponticum that's a problem (only two other species
are recorded from the wild in the UK, and neither is at all common) -
other rhododendrons aren't a problem.

No. It's a result of the media hysteria. If rhododendrons don't
grow well locally, they won't naturalise - and acidity is only one
of the factors that they need. Outside SOME parts of the far west,
and a FEW parts of the south, even R. ponticum will have trouble
when faced with real competition. Despite claims, its spread is
NOT limited by the fact that "it hasn't got here yet", but by the
fact that it won't spread to the relevant locations.

I'm not in the extreme west, but Rhododendron ponticum is moderately
widespread in the wild around here - by my field records about as
widespread as ramsons or butterbur.

On the other hand, outside the extreme west one might want to worry more
about Buddleia davidii and Cotoneaster simonsii, or even Ribes
sanguineum and Syringa vulgaris.

Regards,
Nick Maclaren.

--
Stewart Robert Hinsley

cultivated rhododendros : spreading threat?
 

Thank you very much, Janet, Sacha, Nick, Jeff, and Stewart!

If our cultivated rhodos at our other place had gone and caused saplings
to pop up all over the place, I guess we wouldn't even have considered
growing them here. But confronted with the "authoritative" announcement
of yesterday I was totally unprepared and taken aback. I didn't even
remember in that instant that the rhodies at our previous address had
caused no bother.

Now we shall carefully consider which member of this community to advise
that experienced horticulturalists (all of you!) have assured us there
is no problem and then, fingers crossed, the message will be passed
around! Perhaps we might then see one or two rhodies popping up in
other gardens.

Thanks again.

Eddy.

cultivated rhododendros : spreading threat?
 

The main problem with rhododendrons is that the hybrids that you
purchase in most nurseries are propagated by grafting on to ponticum.
The result is that the ponticum takes over unless they are carefully
watched. I would always when buying rhododendron hybrids to ask the
seller whether they are grafted or propagated on their own roots. My
advice is to REJECT GRAFTED HYBRIDS.

Regards
Don

cultivated rhododendros : spreading threat?
 

Donwill wrote:

The main problem with rhododendrons is that the hybrids that you
purchase in most nurseries are propagated by grafting on to ponticum.
The result is that the ponticum takes over unless they are carefully
watched. I would always when buying rhododendron hybrids to ask the
seller whether they are grafted or propagated on their own roots. My
advice is to REJECT GRAFTED HYBRIDS.

Regards
Don

Many thanks for this interesting info, Don. I've just rung the nursery
where I bought our rhodies and asked them whether their rhodies are
grafted onto Ponticum or propagated on their own roots and they have
assured me that all of the rhodies they sell are propogated. So that's
a relief.

But, just out interest, when you say that in the case of grafted rhodies
the ponticum takes over "unless they are carefully watched", what do you
mean by the "watching"? What is it that one can do in such cases to
stop the Ponticum taking them over?

When I begin instructing those in this area who live in fear of all
rhodies, it would be good to be armed with this knowledge as well and to
be able to speak with what may come across as real expertise! :-)

Thanks.

Eddy.

Look out for branches arising from very low on the plant which have flowers or leaves radically different from the rest of the plant, and cut them out.

You have to do similar with roses which are often grafted on to more vigorous wild species. Or pear trees which throw up quince shoots from the base.

cultivated rhododendros : spreading threat?
 

On 28/05/2010 10:54, Eddy wrote:
Donwill wrote:


The main problem with rhododendrons is that the hybrids that you
purchase in most nurseries are propagated by grafting on to ponticum.
The result is that the ponticum takes over unless they are carefully
watched. I would always when buying rhododendron hybrids to ask the
seller whether they are grafted or propagated on their own roots. My
advice is to REJECT GRAFTED HYBRIDS.

Regards
Don

Many thanks for this interesting info, Don. I've just rung the nursery
where I bought our rhodies and asked them whether their rhodies are
grafted onto Ponticum or propagated on their own roots and they have
assured me that all of the rhodies they sell are propogated. So that's
a relief.

But, just out interest, when you say that in the case of grafted rhodies
the ponticum takes over "unless they are carefully watched", what do you
mean by the "watching"? What is it that one can do in such cases to
stop the Ponticum taking them over?

When I begin instructing those in this area who live in fear of all
rhodies, it would be good to be armed with this knowledge as well and to
be able to speak with what may come across as real expertise! :-)

Thanks.

Eddy.





I'm not an expert Eddy, however, ever since I became interested in
gardening I 've been aware of the dangers of buying hardy hybrids from
nurseries by reading favourite books on the subject.

Ref -Michael Howarth Booth (MHB),The Flowering Shrub Garden, 1947, P59,
"Nursery bought plants are usually grafted on R.Ponticum, which will
cause endless trouble with suckers unless the bushes are planted about 4
inches deeper than before,with peat, only, put on to cover the roots up
to within 2 inches of surface level, and finally a mulch 6 inches deep
of leaves or June cut bracken, put on over all."

Ref - MHB, The flowering Shrub Garden Today, 1961, P77.
"When a bed is planted up solely with grafted hybrid rhododendrons, the
whole thing is apt to be overdone so that we get an overpowering
concentration of flowers at one time and an unrelieved hump of dark
green for the rest of the year. Culturally it is disastrous, for
rhododendron fly and bud blast run riot through such mono-cultures, the
ponticum rootstock smothers the scions unnoticed and eventually a vast
dark catacomb beneath high straggling branches leads to the whole thing
being sooner or later felled to the ground. The ponticum, then,almost
alone survives"
P78.- "if grafted, ponticum suckers are promptly spaded off."

Ref - Cox & Cox, Encyclopaedia of Rhododendron Hybrids, 1988, P10.
" due to the use of the over-vigorous ponticum being used as a rootstock
to graft most hybrids, the rootstock usually throws vigorous suckers
which if left unattended soon smother and kill the hybrid grafted on top."

I've extracted a few ref's above,
MHB recommends spading the suckers off, I'm not sure if that's a bit
drastic, however you could I suppose treat them like rose suckers,
either you cut or pull them off.
I've always planted them a bit deeper than normal, and as an insurance,
any convenient low branch I have layered by abrading the bark and
placing a stone on it to press it down into a bed of acid compost .

Hope this helps
Good Luck.
Don

cultivated rhododendros : spreading threat?
 

Jeff Layman wrote:
"Eddy" wrote in message
...
[...]

Have done a brief google on this subject and found that "Rhododendron
ponticum" can spread.

Thanks.

Eddy.

Most of those big'n'blousy rhodos are hybrids that set little or no
viable seed. They won't spread. Even the true species (other than
ponticum) aren't particularly efficient at spreading by seed in a
short time.

See SRH's comments, authoritative as usual. I'll add my agreement about
R. ponticum's fairly modest rate of increase in any but the most ideal
conditions. Back in West Wales we had them along our little stream, on a
pretty neutral soil. I wish I'd taken notes, but I made a crude estimate
of the age of the oldest (about a hundred years), and, IIRC, deduced
that there may have been no more than about one or two surviving
seedlings per annum. The fields on either side had been stocked for all
that time, so I assume that poaching would have put paid to any
seedlings which tried to extend outward from the stream. An old group
near the house made a delightful den for the children, with the stream
running through.
[...]

--
Mike.